Aleppo, Syria — When informants tipped off Abu Al Hiba to an Islamist Free Syrian Army unit's plan to rob an abandoned wire factory, he immediately dispatched some of his men to guard the factory and told the group that they were urgently needed on the front line. The group, which Mr. Hiba questioned was even a legitimate FSA unit, begrudgingly packed up and went to fight, leaving the factory unmolested.

As head of Revolutionary Security in his neighborhood of Aleppo, Hiba has been tasked with handling such problems and watching over the FSA to make sure its fighters don't commit crimes or violate human rights. The rebel forces' ranks have swelled as what started as a protest movement to remove President Bashar al-Assad became an all-out civil war. With that, the potential for rogue fighters to undermine the FSA's reputation with criminal activity has grown too.

“Revolutionary Security cannot go to a group and just tell them to give up their weapons, stop being rebels, and go home. We have to talk to their commanders," he says, explaining the difficulty of policing the opposition, which often calls for creative solutions.

Members of the FSA and its Syrian supporters now say that the group is no longer composed of those purely interested in overthrowing Assad. Criminal opportunists have entered its ranks or taken up its name, forcing the group to police its own.

“Revolutionary Security was founded two months ago and it’s main mission is to observe the FSA and work with the civilians,” says Capt. Abu Hamdu, chief of Revolutionary Security in Aleppo. “We’re watching and observing the FSA fighters to make sure they don’t make any mistakes dealing with the civilians.”

Far more common, however, are problems with theft. Opposition fighters have been caught looting empty apartments and shops on the front lines and collecting illegal bribes and taxes at checkpoints.

Recognizing the damage such behavior causes to the FSA's image, the group has taken steps to quickly expand Revolutionary Security. In his neighborhood of Aleppo, Hiba now boasts that Revolutionary Security is stronger than the United States' Central Intelligence Agency. His group has recruited, trained, and inserted spies into FSA units throughout the city to report on anyone who violates the law.

The system has been successful in stopping a number of ill-intentioned FSA fighters and units from committing crimes, say Revolutionary Security members. Those who are caught must go before a judge in a revolutionary court, and, if convicted, usually lose their weapons. Sometimes they are even sent to prison. They say that they’ve seen a marked decline in such incidents within the past month, asserting that criminal behavior dropped when word spread that the FSA was monitoring activity.

Revolutionary Security leaders say one of the biggest challenges to carrying out their duties, which include policing civilians, is their own relatively small numbers.

“When the regime was in control there was the state security, military intelligence, Air Force intelligence, and other organizations. Now we’re doing the work of all these organizations,” says Mr. Hamdu.

Hoping to broaden its influence, Revolutionary Security has dispatched religious scholars to FSA units throughout Aleppo to offer courses about appropriate conduct and values.

Ahmad Zayarati, an Islamic scholar and head of Revolutionary Security’s legal section in one neighborhood of Aleppo organizes such courses and also issues fatwas, Islamic legal decisions, to help govern FSA conduct. He and colleagues are also in the process of drafting a law to ensure that detainees are treated with basic human rights and respect.

“We are doing a very important job, which is to make FSA fighters understand that we cannot make an Islamic state with weapons,” says Mr. Zayarati, emphasizing the importance of teaching fighters values.

Gaining trust

Revolutionary Security has struggled to communicate to the civilian population that it’s OK, even encouraged, for them to complain when they see members off the FSA engaged in inappropriate or illegal behavior.

Under the Assad regime, such complaints against the state and government could easily land the whistle blower in jail. Though the revolution was founded on challenging that type of authority, changing the deeply ingrained, 40-year-old culture of not questioning the government remains difficult.

“At the beginning it was difficult for people to break from the culture of fear and complain about the FSA, but then they started going to the Islamists to complain and the Islamists encouraged them to do this,” says Abu Ahmad, a Syrian activist and the head of a relief organization called Eghathet Al Malhouf.

Now he says a growing number of residents feel comfortable approaching Revolutionary Security or the FSA groups themselves to complain. During demonstrations, it’s also not uncommon to hear people criticize corrupt elements of the FSA.

Revolutionary Security represents an important step toward protecting the goals of the revolution from fading away in the midst of the nation’s now violent and chaotic war. They worry, however, that the organization, which grew out of the FSA, is not as critical as it should be of the opposition group.

“Some people in the FSA show up and act like they’re in a higher class because they have weapons and they are fighting,” says Asam Abu Bakar, a barber in Aleppo. Like a number of Aleppo residents, Mr. Bakar complains that many FSA fighters came from the countryside and have different values than those in the city, which often pits them against residents.

When the FSA fighters in his area began firing their weapons in celebration, frightening many residents, he sought out the help of Revolutionary Security.

“I went to complain to Revolutionary Security about this, but some of the Revolutionary Security have ties to the FSA so they won’t do anything,” he says.